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HP XP P9500 User Manual Page 49

Continuous access synchronous for mainframe systems.
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12. In the Minimum Paths box, enter the minimum number of paths necessary for operations to
continue. If the number of paths in Normal status falls below the Minimum Paths value you
set, the main system suspends Continuous Access Synchronous Z pairs. This is done to prevent
a performance drop on the host because of low overall bandwidth between main and remote
system. The default is 1.
If your pairs contain critical data and you are using Continuous Access Synchronous Z
for disaster recovery, set the minimum number to one. This insures that Continuous Access
Synchronous Z operations continue even when there is only one remaining data path.
If performance is a higher priority than critical data, set the minimum number of paths to
two or more (up to eight per CU).
If the pair is suspended because the number of paths has dropped below the Minimum
Paths setting, the M-VOL fence level determines whether write operations continue or are
rejected to the M-VOL.
13. In the RIO MIH Time (sec.) box, enter the amount of time that can pass before the system stops
the copy operation as failed. RIO MIH means "remote I/O missing interrupt handler". The
range of time is from 10 seconds to 100 seconds. The default is 15 seconds.
14. Use FREEZE to enable or disable support for the CGROUP (FREEZE/ RUN) PPRC TSO
command. FREEZE is available only when PPRC support = Yes.
If you select Enable, the main system will accept and perform the CGROUP command.
If you select Disable, the main system will reject the CGROUP command.
Enable FREEZE only after all main-remote paths have been added.
The PPRC commands do not allow you to change the remote system options.
15. In the Round Trip Time (ms) box, enter the time limit for data to travel from the M-VOL to the
R-VOL. This value is used by the system to control initial copy pace when update copying is
in progress.
The default setting of 1 on the P9500 produces a lower than expected initial copy
throughput when the distances involved between the main and remote system cause the RIO
response time to exceed 15 milliseconds.
If the difference between Round Trip Time and the initial copy pace is significant, for example,
1ms RT Time : 500ms initial copy pace, the system slows or even interrupts the initial copy
operation so that the update copy can continue.
Configure disk arrays and define logical paths


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